Project Summary 25.5% of all deaths worldwide can be attributed to infections, suggesting a need for novel therapeutic targets. The mechanisms by which pathogens induce an immune response are well-studied; the ways infections alter metabolism remain largely unexplored. Nevertheless, metabolic dysregulation is clinically observed in a broad range of diseases. The goal of this proposal is to determine the mechanism by which infection disrupts systemic metabolic homeostasis. Understanding the causal relationship between infection and metabolic disruption could lead to novel therapeutics that stabilize metabolism during infection. Here, I propose to use a model of Drosophila melanogaster infected with the bacterial pathogen Listeria monocytogenes. My preliminary analysis identified similar gene expression patterns between infected flies and flies that lack the transcription factor Drosophila Hepatocyte Nuclear Factor 4 (dHNF4). dHNF4 controls insulin signaling and lipid metabolism in mammals as well as invertebrates; these processes are dysregulated in infected flies. The hypothesis driving this work is that dHNF4 mediates the metabolic disruptions that occur in L. monocytogenes-infected flies. In Aim 1, I propose to determine how infection affects dHNF4 regulation by measuring dHNF4 protein levels, post-translational modifications, and activation during infection. In Aim 2, I will determine the role of dHNF4 during infection through gain- or loss-of-function experiments. In Aim 3, I will define the contributions of dHNF4-dependent pathways to infection outcome using an attenuated L. monocytogenes strain. The completion of this work will uncover the relationship between infection and a key metabolic regulator. Furthermore, these studies may inform the development of therapies that target metabolism during infection.